The 22 year-old, who became teetotal in 2010 , admitted his "nightly" drinking sessions became such a "problem" that he went into work drunk.
While he never drank on set, he admitted his alcohol consumption left him "dead behind the eyes".
Radcliffe has acknowledged that he was so desperate to avoid becoming an alcoholic that he now refrains from touching any alcohol.
His latest frank interview comes a few days after he admitted that he “blacked” out nearly every time he drank alcoho l and conceded he was heading down a path of self destruction unless he curbed his drinking habits.
He was so concerned about his behaviour in public when he got drunk that he became “a recluse at 20”, leading to him drinking at home by himself.
In his latest interview, Radcliffe admitted being drunk while on the Harry Potter film sets although he does not disclose which ones.
He has said that his life went off the rails for a period when he turned 18 and was filming Harry Potter and The Half-Blood Prince as the pressures of fame made him so dependent on alcohol.
"I have a very addictive personality. It was a problem," Radcliffe told Heat magazine this week in an interview to promote his latest film.
"People with problems like that are very adept at hiding it. It was bad. I don't want to go into details, but I drank a lot and it was daily – I mean nightly.
"I can honestly say I never drank at work on Harry Potter. I went into work still drunk, but I never drank at work. I can point to many scenes where I'm just gone. Dead behind the eyes."
Radcliffe developed a penchant for whisky and partying, and said he was fortunate that the paparazzi failed to capture his drink-fuelled excess.
Realising he had to change his ways, Radcliffe quit drinking and has not touched a drop of alcohol since August 2010.
"You either have to change something or give into that shame," he added.
The British star, propelled to fame aged 11 after being cast to play the boy wizard in the movies based on J.K. Rowling's bestselling novels, also admits to a "very busy personality".
In the interview he also disclosed that his production-assistant girlfriend, Rosie Coker, was "a wonderful, wonderful girl, who's far too good for me".
"I can also be quite insecure. A lot of actors have self-doubt. I live under that the whole time, and it's how I function best. I think she puts up with a lot; she says she doesn't," said Radcliffe.
Radcliffe has received critical acclaim for his theatre work in the Broadway and West End productions "Equus" and "How to Succeed in Business Without Really Trying".
He is currently promoting his current film, "The Woman in Black", a neo-Gothic horror movie, which opens this week, is his first post-Potter film.
The eight Potter films grossed more than $7.7bn (£4.87 billion) worldwide at the box office and made stars of Radcliffe, Emma Watson and Rupert Grint.